Watches are usually waterproofed by having tightly fitting casing components, with seals where necessary, and a seal around any protruding part such as a stem or winder. While this is sufficient to most purposes, underwater use requires more elaborate procedures. Underwater watches are usually enclosed in a sealed container, with protruding elements separately sealed or enclosed in a flexible or resilient boot.
Solid state digital watches have not been considered particularly suitable for underwater use, since their operating controls usually include from one to three very small push buttons and a recessed setting button. Any sealed enclosure would have to include access or operating connections to the various buttons, which could be easily operated underwater. This is particularly necessary for a diver, since a stopwatch function is often used to time a dive or air supply.